CN111770952B - Method for processing lignocellulosic biomass - Google Patents

Abstract

The present invention relates to a method of treating lignocellulosic biomass, said method comprising the steps of: a. preparing an impregnation liquid (4) comprising a chemical catalyst intended for impregnation of said biomass; b. passing through an impregnation reactor (5) ) into the ground biomass (6), said inlet being located in the first impregnation zone (5a) of the impregnation reactor comprising two overlapping zones, the first impregnation zone and a so-called second dewatering zone (5b) above said impregnation zone; c. introduction of liquid (4a) via a first liquid inlet located in said first impregnation zone (5a) of the reactor; d. via A second liquid inlet in another zone (5d) of the reactor located below the biomass inlet in the first impregnation zone (5b) introduces the liquid (4b) into the reactor. The invention also relates to a device for carrying out the method.

Description

Method for processing lignocellulosic biomass

Field of Invention

The present invention relates to methods of processing lignocellulosic biomass to produce "second generation" (2G) sugar liquors. These sugar liquids can be used to produce other products (eg alcohols such as ethanol, butanol or other molecules such as solvents such as acetone etc.) via biochemical routes. The process generally comprises three steps, namely liquid preparation, impregnation of the biomass and pretreatment of the impregnated biomass, eg by cooking, optionally followed by steam explosion. The present invention focuses more particularly on the first two steps of the method.

current technology

Lignocellulosic biomass represents one of the most abundant renewable resources on Earth. The substrates considered are very diverse, they involve wood substrates such as various woods (hardwood and softwood), by-products from agriculture (wheat straw, rice straw, corncob, etc.) or from other agri-food, paper, etc. industries by-products.

The method for the biochemical conversion of lignocellulosic material to 2G sugar liquor includes in particular a pretreatment step and a step of enzymatic hydrolysis using an enzyme cocktail. These methods typically also include a dipping step prior to pretreatment. The sugar liquor resulting from the hydrolysis is then processed, eg by fermentation, and the method further comprises a separation step and/or a purification step of the final product.

Lignocellulosic biomass consists of three main polymers: cellulose (35%-50%), which is a polysaccharide consisting essentially of hexoses; hemicellulose (20%-30%), which is composed essentially of A polysaccharide composed of pentose sugars; and lignin (15%-25%), which is a polymer with a complex structure and high molecular weight composed of aromatic alcohols linked via ether bonds. These different molecules are responsible for the inherent properties of plant walls and organize themselves into complex tangles.

Among the three base polymers that make up lignocellulosic biomass, cellulose and hemicellulose are the base polymers capable of producing 2G sugar liquor.

Typically, during pretreatment, hemicellulose is primarily broken down into sugars, and cellulose is converted to glucose by enzymatic hydrolysis. However, for enzymes, it is difficult to access crude cellulose, so pretreatment is required. This pretreatment can alter the physicochemical properties of the lignocellulosic material, thereby improving the accessibility of cellulose to enzymes and their reactivity to enzymatic hydrolysis.

There are a number of techniques for carrying out this pretreatment that facilitate the present invention, which will be hereinafter classified under the generic term "cooking": acid cooking, alkaline cooking, steam explosion, "organic solvent pulping" methods. The latter method involves pretreatment in the presence of one or more organic solvents and usually water. The solvent may be an alcohol (ethanol), an acid (eg, acetic or formic acid) or acetone. The "organosolvent pulping" process results in at least partial dissolution of lignin and partial dissolution of hemicellulose. Thus, there are two outlet streams: a pretreated substrate with residual cellulose, hemicellulose and lignin, and a solvent phase containing dissolved lignin and a portion of hemicellulose. There is usually a regeneration step of the solvent, which can extract the lignin stream. Some "solvent pulping" treatments (especially with ethanol) are combined with the addition of strong acids (eg _{H2SO4 )} . It is also conceivable to contact the biomass with a solvent via an impregnation reactor prior to the digestion stage, or contact the biomass with an acidic catalyst prior to performing "organic solvent pulping" digestion.

For example, in the publication "Production of bioethanol from lignocellulosic materials via the biochemical pathway: A review", M. Balat, Energy Conversion and Management 52 (2011) 858-875, or in the publication "Bioethanol production from agricultural wastes: an overview", N Various configurations are reported in Sarkar, S. Kumar Ghosh, S. Bannerjee, K. Aikat, Renewable Energy 37 (2012) 19-27.

One of the most effective pretreatments is acidic steam explosion, which enables almost complete hydrolysis of hemicellulose and significantly improves the accessibility and reactivity of cellulose for enzymes. One or more other processes may be performed before this preprocessing.

Patents US-8057639 and US-8512512 propose a method comprising a first step of hydrolysis of hemicelluloses to C5 sugars under mild conditions which thus protect them from degradation. This step is carried out in the first reactor by injecting steam at a pressure of 1.5 bar or higher, a temperature of 110°C or higher, and optionally in the presence of a weak acid. After this step, washing is performed to extract and recover the C5 sugar liquor, and the remaining biomass rich in cellulose and lignin is then sent to the second step (second reactor) where steam explosion takes place. By injecting high pressure steam, which results in a sudden expansion of the biomass (steam explosion), the second reactor operates at a higher pressure than the first reactor.

Patent application WO-2013/141776 in the field of papermaking describes an impregnation process in a vertical reactor (dimmer) containing an alkaline impregnation liquid, which reactor thus defines a first zone in which the impregnation takes place. The lignocellulosic material is received at the bottom of the macerator and transferred to the top of the macerator by means of two conveying screws. During its transfer to the second zone of the macerator located above the liquid level, the biomass is drained and the liquid falls back into the first zone. In this configuration, the liquid level is controlled by the introduction of alkaline liquid.

The aim of the present invention is to improve the impregnation method and suitable equipment described in the aforementioned application WO-2013/141776.

The present invention is particularly concerned with improving the quality of the impregnation of biomass with catalytic liquids.

Additionally, the present invention seeks to make impregnation methods and equipment easier to use and/or less fluid-intensive.

SUMMARY OF THE INVENTION

The subject of the present invention is first of all a method for processing lignocellulosic biomass, said method comprising the following steps:

a. preparing an impregnation liquid comprising a chemical catalyst intended for impregnation of the biomass, the chemical catalyst being selected from the group consisting of acidic catalysts, basic catalysts and oxidation catalysts, preferably acidic catalysts;

b. Introducing the milled biomass via the inlet of the impregnation reactor, the inlet being located in the first impregnation zone of the impregnation reactor, the impregnation reactor comprising two overlapping zones, the first impregnation zone and a second "drain" zone above said impregnation zone;

c. Introducing liquid via a first liquid inlet located in the first impregnation zone of the reactor.

The present invention is characterized in that the method further comprises the following steps:

d. The liquid is introduced into the reactor via a second liquid inlet in another region of the reactor below the biomass inlet in the first impregnation zone.

In the context of the present invention, a spatial reference of the type "above" or "below" is understood to vary with the preferred vertical direction or inclination with respect to the vertical of the reactor, so that the reactor along its height includes a A series of zones (including an introduction zone followed by a drain zone) through which the biomass fed to the reactor passes. The biomass preferably undergoes an upward movement in the reactor, so the introduction zone is "below" the drain zone. (The invention can be applied to other reactor configurations and these terms apply).

Therefore, the present invention proposes to inject the catalytic liquid into the impregnation reactor not only into the impregnation zone of the reactor (which is conventional), but also below the impregnation zone, below the injection point of the biomass in the reactor. This area is generally considered to be the "dead zone" or "inactive zone" of the reactor, since the biomass introduced into the first impregnation zone will be transported to the drain zone above the impregnation zone, and this upward movement is caused by the Caused by conveying equipment (eg conveying screw). This zone is generally lower in height relative to the other two zones and is located below the first impregnation zone, corresponding to the bottom of the reactor, usually vertically or inclined, through which one or more conveying screws are introduced into the reactor, The movement of the conveyor screw is driven by an electric motor. Injecting liquid into this area is contrary to conventional practice, as there is little/no biomass staying in this area, and if fluid injection into this area is envisaged, the fluid (if any) is only possible using a delivery screw in the reactor In the case of water intended to lubricate the screw (so basically for mechanical purposes).

It has now turned out unexpectedly that the injection of catalytic liquid into this zone below the injection point of the biomass in the reactor is particularly beneficial for the impregnation process. In fact, it was indirectly demonstrated by comparative measurements of the yields at the end of the steam explosion pretreatment carried out after the impregnation treatment that for an equivalent amount of catalyst consumption (i.e. not excessive consumption of catalytic liquid, but by injecting catalytic liquid into two different zones of the reactor rather than injecting into one zone), the impregnation of the biomass proceeds more successfully.

The reasons for this improved impregnation may be various: liquid injected below the biomass injection point may allow better treatment of the biomass just in its injection zone. In practice, for injecting biomass, it is often possible to use a feed screw which compresses and conveys the biomass into the reactor, the biomass plug formed in the downstream part of the screw preventing liquid backflow to the upstream end of the screw. Furthermore, the biomass plug is mechanically broken upon entering the reactor, in particular by using a piston, which meets the biomass plug in question in the reactor. Injecting the liquid just below the area where the biomass plug breaks seems to be very beneficial to allow the catalyst to impregnate the biomass "earlier" during the delivery of the biomass in the reactor, thereby achieving, for the same reactor residence time, for a better, more complete impregnation. In addition, it has been found that the liquid thus injected is a perfect substitute for any wash water used to lubricate screw-type biomass conveying equipment in the reactor.

Other advantages of the present invention: Better results are obtained without additional consumption of catalyst. The equipment is simplified, as there is no need to provide a separate water supply at the bottom of the reactor, but rather the liquid is withdrawn from its preparation zone. Limiting the addition of water to the reactor is also beneficial to limit the dilution of the catalytic liquid in the reactor, thus limiting the need, if any, to readjust the catalyst content in the liquid, for example.

Advantageously, and as previously described, the biomass is conveyed from the first impregnation zone to the second draining zone by means of conveying means, such as one or more conveying screws. In the first zone, the biomass becomes impregnated with liquid and is drained in the second zone. The conveying screw of the drain area may be surrounded by a grid through which excess liquid flows out.

It is also advantageous that the biomass is introduced into the first impregnation zone of the reactor by means of a feed device that produces a biomass plug that prevents the backflow of liquid from the first zone into the feed device, so that The feeding device is in particular a feeding screw.

Thus, according to the present invention, the liquid produced from the same preparation zone is injected into two points, and for a given liquid consumption, the proportion of liquid injected into the impregnation zone relative to the liquid injected below the biomass injection point can be metered : preferably, 80%-98% by volume, in particular 85%-90% by volume of the liquid introduced into the impregnation reactor is introduced via the first liquid inlet, the remainder to 100% of the liquid introduced into the reactor is introduced via The second liquid inlet is introduced. Therefore, most of the liquid is injected into its normal zone, "withdrawing" up to 20% of this amount to inject it into the bottom of the reactor.

The introduction of liquid via the first liquid inlet and/or via the second liquid inlet can be carried out continuously or discontinuously.

Preferably, the other region of the reactor where the second liquid inlet is located is an inactive region located at the bottom of the reactor which is placed substantially vertically or inclined with respect to the vertical.

According to a preferred embodiment, the liquid used is an acidic catalytic liquid, and the pH of said liquid is adjusted to 0.1-4, especially 0.3-2.

Examples of the acid that can be used include at least one acid selected from sulfuric acid, hydrochloric acid, nitric acid, and oxalic acid. Their content in the aqueous phase is preferably 0.2% by weight to 8% by weight.

Another subject of the present invention is a method for the continuous processing of lignocellulosic biomass, which comprises the aforementioned steps and continues continuously or discontinuously by comprising the steps of:

e. transferring the impregnated and drained biomass from the impregnation reactor outlet to a digestion reactor, optionally in combination with steam explosion;

f. pretreating the biomass in the reactor;

g. Enzymatic hydrolysis of the pretreated biomass;

h. Alcohol fermentation of enzymatically hydrolyzed unfermented juice (must) obtained from pretreated biomass.

Another subject of the present invention is a lignocellulosic biomass processing plant comprising:

- a zone equipped with a liquid outlet for the preparation of the impregnation liquid containing chemical catalysts for the impregnation of the biomass, in particular acidic catalysts, basic catalysts or oxidation catalysts, preferably acidic catalysts;

- an impregnation reactor comprising a first impregnation zone equipped with a biomass inlet and a second zone, called a drain zone, superposed on said first impregnation zone and equipped with a biomass outlet;

- a device for feeding the milled biomass to the impregnation reactor via the biomass inlet of the reactor located in the first impregnation zone;

- a first device for feeding the impregnation liquid to the reactor, said device connecting the liquid outlet of the liquid preparation zone to the first liquid inlet in the first impregnation zone of the reactor;

The device also includes:

- a second device for feeding the impregnation liquid to the reactor which connects the liquid outlet of the liquid preparation zone to a second liquid inlet in the reactor zone below the biomass inlet of the first impregnation zone.

By providing means for introducing the catalytic liquid into the second point of the impregnation reactor, the apparatus can carry out the aforementioned method.

It should be noted that the present invention also includes injecting catalytic liquid into the impregnation reactor at points other than two injection points, such as via three or four different inlets, including at least one of the impregnation zones, such as Two inlets and at least one below the biomass injection point, eg one or two inlets.

The device according to the invention preferably uses impregnation reactors oriented vertically or obliquely with respect to the vertical direction, by means of one or more conveying screws in the reactors placed in said zone, the biomass undergoes a passage from the first impregnation zone to the second impregnation zone. The rising movement of the second row of dry areas.

The impregnation liquid preparation zone can be a tank, a static mixer or a dynamic mixer or any other device that can mix a solvent (eg water) and a catalyst (eg _acid in the case of acidic liquids, eg _H2SO4 ).

According to a first embodiment, the first and second liquid feed devices comprise a common line section connected to the same liquid outlet of the liquid preparation zone: a bypass is formed on the line to supply liquid to the impregnation zone of the reactor.

According to another embodiment, the first and second liquid feed devices are each connected to a different outlet of the liquid preparation zone: a completely separate line is then used to transport the liquid from the other outlet to the second liquid inlet of the reactor.

As already mentioned, the biomass feeding device is preferably designed to produce a biomass plug that prevents backflow of liquid from the first zone into the feeding device, in particular the feeding screw.

The plant according to the invention may additionally comprise a reactor for pretreating the biomass obtained at the outlet of the maceration reactor, an enzymatic hydrolysis reactor and an alcohol fermentation reactor, the reactor group or at least two of which are installed in series .

Another subject of the invention is the aforementioned method or device for the treatment of biomass, such as wood, straw, agricultural residues and all dedicated energy crops, in particular annual or perennial plants such as Miscanthus, for the production of sugars, biofuels or biobased molecules use. More generally, the lignocellulosic biomass or lignocellulosic material used in the method according to the invention is obtained, for example, from logs or processed wood (hardwood and softwood), agricultural by-products (eg straw), plant fibers, forestry crops, from Residues of alcohol-producing, sugar- and cereal-producing plants, residues from the paper industry, marine biomass (eg cellulosic macroalgae) or conversion products of cellulosic or lignocellulosic materials. The lignocellulosic material can also be a biopolymer and is preferably rich in cellulose.

Preferably, the lignocellulosic biomass used is wood, wheat straw, wood pulp, miscanthus, rice straw or corn stover.

Detailed description

The invention will be described in detail below by means of non-limiting examples illustrated by the following figures:

- Fig. 1: Schematic diagram of a plant for impregnating biomass with a liquid according to the prior art;

- Figure 2: a general schematic diagram of the type of block diagram of the impregnation apparatus and method used in the present invention;

- Figure 3: An overview schematic of the block diagram type of the complete plant and process from biomass impregnation as shown in Figure 2 to continuous conversion of biomass to ethanol.

Figures 1 to 3 are described using the following reference numbers, which correspond to the same components/fluids/products throughout:

1: Water enters the liquid preparation tank

2: Acid enters liquid preparation tank

3: Liquid preparation equipment (tank)

4: Acidic liquid

4a: Acidic liquid enters impregnation equipment (reactor) (injection via impregnation zone)

4b: The acidic liquid enters the impregnation equipment (reactor) (injected into the bottom to lubricate the conveying screw)

5: Impregnation equipment (reactor)

5a: Impregnation zone of the impregnation reactor

5b: Drainage zone of the immersion reactor

5c: The screw that transports the biomass into the impregnation reactor

5d: impregnation reactor zone located below impregnation zone 5a (below point 6b where biomass enters reactor 5 through feed screw 6a)

6: Grind biomass

6a: Conical screw feeding biomass to the impregnation reactor

6b: Biomass sealing plug in feed screw 6a

7: Impregnated and drained biomass

8: Screw feeder or plug-screw feeder for pretreatment equipment

9: Pretreatment equipment (blasting reactor)

10: The squeeze liquid of the screw 8 of the pretreatment equipment

11: Inject steam for pretreatment

12: Pretreated biomass and steam

13: Equipment for the separation of steam and pretreated biomass (cyclones)

14: Steam condensation

15: Pretreated biomass

16: Enzymatic hydrolysis

17: Enzymatic hydrolysis of unfermented juice with sugar

18: Alcohol (ethanol) fermentation

19: Fermented wine (alcohol) containing ethanol

20: Distillation

21: Concentrated alcohol

22: Crude lees.

Figure 1 is a schematic diagram of an apparatus employing liquid-impregnated biomass according to the prior art; therefore, it is not necessarily drawn to scale and does not represent all components of the apparatus, but only those of more particular interest for describing the present invention.

The method according to the present invention is a method of treating lignocellulosic biomass prior to enzymatic hydrolysis. It is integrated into methods involving the production of second-generation sugars from which oxygen-containing molecules (eg, alcohols such as ethanol, butanol, etc.) can be obtained through a number of biochemical pathways.

Thus, the following examples relate to an integrated acid impregnation process followed by continuous or discontinuous steam explosion pretreatment, optionally with recirculation of the acid impregnation liquid.

This method is compatible with methods for producing 2G sugars (ie those obtained from lignocellulosic biomass) or more broadly biobased molecules (ie molecules from or derived from natural matrices).

Biomass and Transfer Area

Depending on the biomass (straw, wood, etc.), a grinding step is required to make the particle size compatible with the technical means and operating conditions of the step. For this, simple chopping may be sufficient, but grinding with or without refining may be required.

Typically, the milled biomass 6 has a particle size (maximum dimension) of not more than 300 mm. Usually, 5-100mm screen mesh is used to grind the straw, and the wood is chopped into cuboid chips, the length of which is 20-160mm, the width is 10-100mm, and the thickness is 2-20mm.

The milled biomass 6 is introduced into the first impregnation zone 5a of the impregnation reactor via a conical feed screw 6a, in which a sealed biomass plug 6b prevents liquid from escaping from the entire first impregnation zone just before entering the first impregnation zone. The zone 5a flows back into the spiral 6a. The conical compression screw may comprise a shroud in the form of a perforated grid. It has a conical part connected to the bottom of the first impregnation zone 5a of the reactor. Thus, this screw 6a serves a dual purpose: first, to continuously introduce biomass into the impregnation reactor, and second, to form a biomass plug to achieve tightness and prevent leakage of liquid from the impregnation reactor to the screw and upstream of the screw.

Impregnation step

The immersion is carried out at atmospheric pressure and at a temperature of 10-95°C. The residence time of the biomass in the impregnation reactor 5 is typically 20 seconds to 60 minutes, preferably at least 30 seconds, preferably at least 1 minute, preferably no more than 45 minutes, and typically 1-35 minutes. Preferably, it is carried out in a single reactor.

The impregnation reactor 5 (or the impregnator) is tubular and has an inclined orientation to the vertical or at an angle of less than 60° with respect to the vertical. In the example it is vertical. The reactor comprises two superimposed impregnation zones 5a, 5b on the same axis. The lower zone 5a is referred to as the first impregnation zone and receives the compressed biomass from the feed screw 6a via an orifice above which there is provided the sour liquid inlet 4 still in this first zone 5a. The upper zone 5b (top zone) is called the second impregnation zone or drain zone: it receives biomass from the first impregnation zone 5a.

The reactor 5 (macerator) is equipped with one or more conveying screws 5c, which transfer the biomass via the top of the second maceration zone 5b to the outlet orifice via the bottom of the first maceration zone.

The first impregnation zone 5a (and thus the zone where impregnation takes place) corresponds to a space filled with impregnation liquid. The second impregnation zone 5b does not contain any continuous liquid phase. It is particularly advantageous to maintain a constant distribution between the first impregnation zone and the second impregnation zone. For this purpose, the reactor is equipped with a detection system (liquid level sensor), preferably with a system for adjusting the liquid level (not shown), which can ensure filling to the desired liquid level.

The catalytic impregnation liquid is an aqueous solution with a pH of 0.1-6, preferably 0.2-4.0 and a temperature of 10-95°C. The acid here is sulfuric acid. Liquids of this type are well known to those skilled in the art, and any other acid commonly used for impregnation is suitable for use. The amount of acid and the temperature of the liquid are usually fixed. Means for obtaining and maintaining the temperature are known to those skilled in the art. The preparation of the liquid here takes place in tank 3 with water inlet 1 and concentrated sulfuric acid inlet 2 .

The effect of compressing the biomass during the formation of the biomass plug (at the height of the conveying screw), and the effect of decompression at the inlet of the first impregnation zone filled with liquid, allows for better saturation of the biomass (sponge effect). The biomass is transferred through a first zone 5a where it is impregnated towards a second impregnation zone 5b located above the liquid level.

In the second impregnation zone 5b, a portion of the impregnation liquid is separated from the impregnated biomass by draining off during the ascent to the second impregnation zone, the drained liquid falling back into the first impregnation zone 5a.

Preferably, the second impregnation zone 5b is equipped with one or more screens that retain the wet biomass in the second impregnation zone, which screens thereby allow liquid to flow from the second impregnation zone 5b to the first impregnation zone 5a.

Upon leaving the second impregnation zone and impregnation reactor, the impregnated and drained biomass is recovered and contains little or no free water. Its solids content is usually 15% to 40% by weight.

A separated liquid, commonly referred to as waste liquid, is found in the liquid in the first impregnation zone.

Preparation of Immersion Liquid

Liquid and acidity is lost due to maceration. It is therefore necessary to regularly add fresh acidic liquid.

These additions make it possible to precisely adjust the liquid level in the impregnation reactor.

Liquid preparation is also a step in which its operating parameters such as temperature, pH or any other characteristic can be adjusted. The appropriate acid concentration is adjusted by the input of acid and/or water. Homogeneous liquids can also be produced. This step is carried out in the liquid preparation zone.

Various equipment can be used, for example here a mixing tank or a mixer (preferably a static mixer) equipped with a stirring system (not shown).

Preferably, the device is equipped with sensors for measuring pH and flow of water, acid and prepared liquid, etc. All these sensors together can implement balanced flow and acidity control, resulting in stable continuous operation under the desired conditions.

The liquid preparation tank 3 and/or the immersion reactor 5 are equipped with heating equipment such as jackets, coils (and optionally located adjacent to or directly at the equipment (tanks, mixers, etc.) , mixers, etc.) on the optional liquid recirculation loop (exchanger on the loop) for heating.

The liquid tank 3 is connected to the impregnation reactor via one or more liquid transfer lines.

Thus, a liquid can be prepared at a suitable concentration and a suitable flow rate, which can achieve a defined pH (or any other characteristic), which can be an adjusted nominal value.

The invention arises from the following observation: Still in Figure 1, in the impregnation reactor 5, it is noted that there is a third zone 5d below the introduction height of the biomass plug 6b, below the first impregnation zone 5a: this is a "dead zone" ” zone because no desired biomass passes through at that location. This dead or "inactive" zone is necessary to allow room for expansion of the biomass plug and to limit the accumulation of solids at the bottom of the reactor. This region 5d consists essentially of liquid, since it lies outside the channel required for solids. However, given the deviation from the ideal situation of piston delivery by ascending screw 5c, and given the presence of particles in the biomass plug, a small fraction of solids may be observed in the dead zone. Now, it is desirable to avoid the accumulation of solid components in this region 5d.

It is therefore chosen to inject a fluid into this zone 5d, which is not a simple supply of water (water would cause additional dilution of the liquid in the reactor), but an additional supply of liquid from the preparation tank 3, as described in Figures 2 and 2 below 3 shown.

According to Figure 2, acid and water are introduced into the acid liquid preparation tank 3 via line 1 and line 2, respectively. The acidic liquid from line 4 is then injected into macerator 5, where it is mixed with the milled biomass introduced into the process via line 6. The acidic liquid 4 is injected into the impregnation tank 5, more precisely into the impregnation zone 5a, by means of the lines 4a and 4b. The biomass in contact with the acidic liquid in the impregnation zone 5a then enters the drain zone 5b for separation from the liquid fraction. The soaked and drained biomass is transferred via line 7 to the next step of the process.

In this embodiment of the invention, it is chosen to add an additional line 4b for supplying liquid to the region 5d below the biomass feed point of the reactor 5, here the line 4b is connected to the inlet of the tank 3 Form of bypass line for main line 4-4a. It goes without saying that any other piping arrangement is also possible which also conveys the liquid to the bottom of the reactor, in particular by alternatively providing a dedicated line connecting the second outlet of the tank to the inlet of the region 5d of the reactor 5, or by using Any other system that distributes liquid from tank 3 to two separate inlets of reactor 5. A device is provided for regulating the amount of liquid injected into the impregnation zone 5a relative to the amount injected in the zone 5d, and said device is known from the prior art (regulator valve, etc.).

Figure 3 shows the process of Figure 2 continuing after maceration by successive steam explosion pretreatment and then through several other successive processing steps until alcohol fermentation.

The process is therefore carried out in the following way: the impregnation is carried out in the reactor 5 as shown in FIG. 2 and will therefore not be described again.

Once the biomass has been impregnated and drained, the biomass is transferred via line 7 and introduced into the steam explosion pretreatment unit 9 by means of a conveying screw 8 capable of compressing the biomass to form a biomass plug. During this compression, solid/liquid separation occurs and the spent acidic liquid 10 is discharged through the perforated area of the spiral. Optionally, the spent acidic liquor 10 , also referred to as press liquor, can be at least partially recycled by reintroducing it into the liquor preparation tank 3 . The biomass is then processed in the processing plant 9 . Steam is introduced into pretreatment reactor 9 via line 11 . Acid digestion and steam explosion are carried out in this reactor. Explosive expansion takes place and the mixture 12 of pretreated substrate and steam is sent to a separation device 13 of the cyclone type.

It should be noted that in this example, steam explosion is performed after cooking, but steam explosion is still optional and other treatments than cooking are possible for the purpose of this pre-treatment, i.e. changing (via at least one physicochemical property of the impregnated) biomass, such as its degree of polymerization or crystallinity. These other cooking treatments have been mentioned above. The operating conditions for the cooking, which are acidic here, are for example as follows: the plant 9 comprises a cooking zone in which the biomass is contacted with steam for 1-30 minutes with a specific steam consumption of 0.05-10 t/t biomass solids, Said zone has a temperature of 150-250°C and a pressure of 0.5-4 MPa, followed by a zone to expand the biomass obtained from the cooking zone, followed by a zone to separate the steam from the biomass. Preferably, the conditions are adjusted to limit the cooking time to 1-30 minutes. Typically, the specific steam consumption is 0.05-10 tons/ton solids. The recovered steam is advantageously recycled to the steam explosion step after compression, or optionally to on-site utilities. Here, this step is carried out in the reactor 9, which is tubular and horizontal (can also be slightly inclined to allow the liquid to flow) and is equipped with a biomass conveying screw. At the downstream end of the reactor 9, the biomass is very rapidly entrained by the steam to the expansion zone in a line called the blowline, which has a reduced diameter relative to the digestion zone.

In the plant 13 the steam 14 is separated from the pretreated biomass 15 . The pretreated biomass is then converted in a conversion plant 16 into an enzymatically hydrolyzed unfermented juice (must) 17 containing sugars using an enzyme mixture. The sugars are converted to alcohols (eg: ethanol, acetone, butanol) by fermentation in fermentation step 18. The fermented wine 19 is sent to the separation and purification step 20 . A step 20 , for example by distillation, can achieve the separation of the concentrated alcohol-containing stream 21 from the distillers grains (wastewater, residual lignin) 22 . Conditions for enzymatic hydrolysis and for continuous or simultaneous fermentation are appropriate for the desired product and are known to those skilled in the art.

It should be noted that, with respect to Figure 2, the invention applies equally and with the same advantages to a process in which some or all of the steps following steam explosion are not carried out continuously but in "batch" or "batch feed" mode.

Example

In the examples described below, the abbreviation "SC" denotes the solids content, which is determined according to the standard ASTM E1756-08 (2015) "Standard Test Method for Determination of Total Solids in Biomass".

Example 1 (comparison)

This example relates to a method of impregnating and pre-treating wood having the following characteristics:

Raw material: Poplar, flow rate 6.79 t/h, solid content SC: 55.6%, average composition (based on SC):

% (based on SC) cellulose 42.6% Hemicellulose 20.5% Lignin and others (ash, extractables, etc.) 36.9%

The wood was used in chip form with a characteristic size of 50mm. The temperature of the chips entering the unit is room temperature.

The chips are conveyed to the impregnation reactor 5 via the conical screw 6a. The impregnation reactor 5 is a vertical tube in which the biomass 6b is transported vertically by two counter-rotating screws 5c in series. The total working volume of the reactor was 1.95 m ³ . The screw speed and liquid level were adjusted to ensure a dwell time of 30 seconds in the impregnation zone and a drain time of 60 seconds.

The following were introduced into impregnation reactor 5:

- compressed wood chips via the conical conveying screw 6a,

- 2.5 t/h acidic liquid prepared with water and sulphuric acid with a mass concentration of 1.76% by weight at a temperature of 90°C,

- At a temperature of 20°C, 0.3 t/h of water was introduced into the bottom of the impregnation reactor 5 in zone 5d to lubricate the vertical conveying screw 5c.

The impregnated debris is removed from impregnation reactor 5 and transferred to steam explosion reactor 9 . The steam explosion pretreatment was carried out at 200°C in the continuous configuration described above and with a short residence time. The medium suddenly expands to a pressure of 1.3 atmospheres.

The pretreated matrix thus obtained had a free xylose content of 6.9% (SC based) and a potential xylose content (monomers, oligomers and polymers) expressed as xylose of 14.5% (SC based). ). _The impregnation consumed 44 kg of pure _H2SO4 /hour, ie 11.65 kg of pure acid per ton of substrate SC. The degree of xylose release, expressed as a percentage of xylose in free form relative to the total latent xylose, was 47.6%.

Example 2 (according to the invention)

This example uses the impregnation method and the wood pretreatment method according to the invention, treating the same raw material as in Example 1.

The chips are conveyed to the impregnation reactor 5 via the conical screw 6a. Impregnation Reactor 5 was the same as in Example 1. The speed and level of screw 5c were adjusted to ensure a dwell time of 30 seconds in the impregnation zone and a drain time of 60 seconds. The following were introduced into impregnation reactor 5:

- compressed wood chips via the conical conveying screw 6a,

- 2.5 t/h acidic liquid prepared with water and sulfuric acid with a mass concentration of 1.57% by weight at a temperature of 85° C. via an inlet located in the impregnation zone 5a,

- Introducing 0.3 t/h of the same acidic liquid into the bottom of the impregnation reactor 5 at a temperature of 85°C; in the zone 5d located below the injection point of the biomass 6 in the reactor.

The impregnated chips are removed from the impregnation reactor 5 and transferred continuously to the steam explosion reactor 9 via the feed screw 8 . The steam explosion pretreatment was performed in the same manner as in Comparative Example 1.

The pretreated matrix thus obtained had a free xylose content of 11.1% (SC based) and a potential xylose content (monomers, oligomers and polymers) expressed as xylose of 15.1% (SC based). ). _The impregnation consumed 44 kg of pure _H2SO4 /hour, ie 11.65 kg of pure acid per ton of substrate SC. The degree of xylose release, expressed as a percentage of free form xylose relative to the total latent xylose, was 73.5%.

An accurate and reliable measurement of the quality of the biomass with liquid impregnation leaving the impregnation step does not yet exist, but this quality can be indirectly assessed by the xylose content obtained at the end of the steam explosion pretreatment in reactor 9 according to Figure 2 . It should be noted that the advantages of the present invention are also retained if the impregnation step and the steam explosion pretreatment step are performed discontinuously in a "batch" fashion.

By comparing the results of Example 1 and Example 2, it can additionally be seen that the present invention allows better release of xylose in the pretreated matrix with the same acid consumption by additionally injecting liquid into the bottom of the reactor , all factors are otherwise equal, thus demonstrating better impregnation of the biomass: the value shifts significantly from a free xylose content of 6.9% to a free xylose content of 11.1%, which means that with the present invention , almost twice as much xylose can be released from the same biomass without consuming more acid, with completely modest changes to the method and equipment, and is easy to implement using existing equipment on the production line.

Example 3 (according to the invention)

In this example, straw is treated with a method for converting lignocellulosic biomass to ethanol according to the present invention. The straw used has the following characteristics:

Raw material: natural straw, flow rate 3.36 tons/hour, solid content SC: 85.6%, average composition (based on SC):

% (based on SC) cellulose 36.0% Hemicellulose 26.8% Lignin and others (ash, extractables, etc.) 37.2%

The straw is ground on a 50mm screen and then conveyed to the impregnation reactor 5 through the conical screw 6a. The following were introduced into impregnation reactor 5:

- the compressed straw via the conical conveying screw 6a,

- 14.53 t/h of acid liquid prepared in acid liquid preparation tank 3 at a temperature of 75°C,

- The same acidic liquid was introduced into the bottom of the impregnation reactor at 0.57 t/h at a temperature of 75°C, in zone 5d located below the biomass introduction point in the reactor.

The impregnated straw is removed from the impregnation reactor 5 and transferred into the conical conveying screw 8 , which ensures the introduction of the impregnated straw into the steam explosion reactor 9 . During the entry of the impregnated straw into the conical conveying screw, a juice called press liquor is extracted at an average flow rate of 9.74 t/h, which is mixed with water for external washing of the conical screw, and the total collected The flow was 10.59 tons/hour, of which 85% was recycled. Steam explosion pretreatment was performed at 185°C in a continuous configuration with short residence times. The medium suddenly expands to a pressure of 1.3 atmospheres.

The acidic liquid delivered to the impregnation reactor is prepared in the acidic liquid tank by mixing:

- Partially recirculated press liquor with a flow rate of 9 t/h,

- 96 wt% _{H2SO4 acid} supplied at a flow rate of 0.126 t/h,

- Water supplied at 5.973 tons/hour.

The press liquor 10 is extracted from the feed screw of the pretreatment blast reactor 9 and, in this example, collected and pumped to the liquor preparation tank 3 for recirculation therein. Thus, in this example, the mixing tank 3 is fed via a water supply line 1, a line ₂ for a concentrated _H2SO4 acid solution and an additional line (not shown in the figure) for conveying the recirculated press liquor 10.

The so obtained pretreated matrix had a free xylose content of 15.9% (SC based) and a potential xylose content (monomers, oligomers and polymers) expressed as xylose of 21.8% (SC based). ).

The pretreated substrate is then sent to reactor 16 for simultaneous enzymatic hydrolysis and fermentation. To achieve the desired operating conditions, the enzyme mixture stream, yeast stream and water stream were added to the substrate in a total amount of 4.85 tons/hour. The enzyme mixture is produced by a fungus of the genus Trichoderma reesei, and the yeast used is a yeast of the Saccharomyces cerevisiae type genetically modified to consume xylose. At the end of the reaction, the medium contained ethanol at a concentration of 47 g/kg. The wine 19 is sent to the separation unit 20, whereby a stream of ethanol having a concentration of 99.7% by weight can be obtained by distillation and dehydration. The flow rate of this ethanol stream was 0.552 tons/hour.

For straw type biomass, it is also effective to inject additional liquid into the bottom of the impregnation reactor.

Claims (21)

1. A method for processing lignocellulosic biomass (6), the method comprising the steps of: a. preparing an impregnation liquid (4) comprising a chemical catalyst intended for impregnation of the biomass, the chemical catalyst being selected from the group consisting of acidic catalysts, basic catalysts and oxidation catalysts; b. Introducing the milled biomass via the inlet of the impregnation reactor (5) located in the first impregnation zone (5a) of the impregnation reactor comprising two overlapping zones, i.e. said first impregnation zone and a second "drain" zone (5b) above said impregnation zone; c. introduction of liquid (4) via a first liquid inlet located in said first impregnation zone (5a) of the reactor; It is characterised in that the method further comprises the following steps: d. The liquid is introduced into the reactor (5) via a second liquid inlet in another zone (5d) of the reactor located below the biomass (6) inlet in the first impregnation zone (5b). 2. The method according to claim 1, characterized in that the biomass (6) is conveyed from the first impregnation zone (5a) to the second draining zone (5b) by means of one or more conveying screws (5c), The biomass is impregnated with a liquid in the first zone and drained in the second zone. 3. The method according to claim 1 or 2, characterized in that the biomass (6) is introduced into the first impregnation zone (5a) of the reactor by means of a feeding device (6a) which produces a preventive Liquid flows back from the first zone (5a) to the biomass plug (6b) in the feed device (6a). 4. The method of claim 3, wherein the feeding device is a feeding screw. 5. The method according to claim 1 or 2, characterized in that 80%-98% of the liquid introduced into the impregnation reactor (5) is introduced via the first liquid inlet (4a), and is The remainder to 100% of the liquid introduced into the reactor is introduced via the second liquid inlet (4b). 6. The method according to claim 1 or 2, characterized in that 85%-90% of the liquid introduced into the impregnation reactor (5) is introduced via the first liquid inlet (4a), and is The remainder to 100% of the liquid introduced into the reactor is introduced via the second liquid inlet (4b). 7. The method according to claim 1 or 2, characterized in that the introduction of liquid via the first liquid inlet (4a) and/or via the second liquid inlet (4b) is carried out continuously or discontinuously. 8. The method according to claim 1 or 2, characterized in that, another area (5d) of the reactor (5) where the second liquid inlet is located is located substantially vertically or with respect to the vertical direction The inactive zone at the bottom of the reactor is slanted. 9. The method according to claim 1 or 2, characterized in that the liquid (4) is an acidic catalytic liquid, and the pH of the liquid is adjusted to 0.1-4. 10. The method according to claim 1 or 2, characterized in that the liquid (4) is an acidic catalytic liquid, and the pH of the liquid is adjusted to 0.3-2. 11. A method for the continuous processing of lignocellulosic biomass, characterized in that it comprises the steps of any one of claims 1-10, and continues continuously or discontinuously by comprising the steps of: e. Transfer the impregnated and drained biomass from the impregnation reactor outlet (5) to the digester pretreatment reactor (9); f. pretreating the biomass in the digestion reactor (9); g. Enzymatic hydrolysis (16) of the pretreated biomass (15); h. Alcoholic fermentation (18) of enzymatically hydrolyzed unfermented juice (17) obtained from pretreated biomass. 12. An apparatus for processing lignocellulosic biomass, comprising: - a zone (3) equipped with a liquid outlet for the preparation of an impregnation liquid (4) comprising a chemical catalyst for the impregnation of the biomass, the chemical catalyst being selected from acid catalysts, basic catalysts or oxidation catalysts; - an impregnation reactor (5) comprising a first impregnation zone (5a) equipped with a biomass inlet and a second, called drain zone, superposed on said first impregnation zone and equipped with a biomass outlet area (5b); - a device (6a) for feeding the milled biomass to the impregnation reactor (5) via the biomass inlet of the reactor located in the first impregnation zone (5a); - feeding the impregnation liquid to a first device (4a) of the reactor (5) which connects the liquid outlet of the production zone (3) of the liquid (4) to the first impregnation zone of the reactor liquid inlet; It is characterised in that the device further comprises: - feeding the impregnation liquid to a second device (4b) of the reactor (5) which connects the liquid outlet of the liquid preparation zone (3) to the reaction located below the biomass inlet of the first impregnation zone (5a) A second liquid inlet in the vessel region (5d). 13. Apparatus according to claim 12, characterized in that the impregnation reactor (5) is oriented vertically or obliquely with respect to the vertical, by means of one or more of the zones placed in the reactor A conveying screw (5c) subjects the biomass to an upward movement from the first impregnation zone (5a) to the second draining zone (5b). 14. Apparatus according to claim 12 or 13, characterized in that the impregnation liquid preparation zone is a tank (3) or a static mixer or a dynamic mixer. 15. Apparatus according to claim 12 or 13, characterised in that the first liquid feeding device and the second liquid feeding device comprise a common line connected to the same liquid outlet of the liquid preparation zone (3) Section (4), or the first and second liquid feed devices are each connected to different outlets of the liquid preparation zone (3). 16. Apparatus according to claim 12 or 13, characterised in that the biomass feeding device (6a) produces a biomass plug (6b) preventing backflow of liquid from the first zone into the feeding device ). 17. The apparatus of claim 16, wherein the feeding device is a feeding screw. 18. The device according to claim 12 or 13, characterized in that the device further comprises a pretreatment reactor (9) for the biomass obtained at the outlet of the impregnation reactor (5), an enzymatic hydrolysis reaction A reactor (16) and an alcohol fermentation reactor (18), all or at least two of which are installed in series. 19. Use of the method or apparatus of any of claims 1-18 for processing biomass (6) for the production of sugars, biofuels or biobased molecules. 20. Use according to claim 19, characterised in that the biomass (6) is wood, straw, agricultural residues or all dedicated energy crops. 21. The use of claim 20, wherein the dedicated energy crop is Miscanthus.

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